Antenna



FIG. 1 is a front elevation view of an antenna;

FIG. 2 is a side plan view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is top perspective view thereof;

FIG. 5 is a front elevation view thereof; and,

FIG. 6 is a top plan view thereof.

The broken lines showing a base in FIGS. 1-4 represent environment and form no part of the claimed design. 

CLAIM The ornamental design for an antenna, as shown and described. 